Defining Equipment Reliability

Transcription

1 1 Paul Barringer, P.E. Barringer & Associates, Inc. P.O. Box 3985 Defining Equipment Reliability Humble, TX Phone: Reliability measures the capacity of equipment or processes to operate without failure for a time interval when put into service and operated correctly. 2 Reliability Is? Reliability is concerned with avoiding failures of equipment and processes by proper design and careful operation of the equipment by trained personnel in a specified environment for a given time interval. The ultimate aim of reliability is a failure free environment. MIL-HDBK-338: Reliability- 1) The duration or probability of failure-free performance under stated conditions. 2) The probability that an item April can 18, 2006 perform its intended function for a specified interval under stated conditions. 1

2 3 Which Is More Important? Avoiding failures OR fixing failures? You cannot repair yourself to happiness! Equipment OR processes? Equipment = pawns, Processes = king Trained operators OR maintainers? Untrained operators can break equipment faster than trained maintainers can repair 4 Maintenance Is? Maintenance is concerned with retaining function or quickly correcting failures, by use of trained employees using correct procedures. The ultimate aim of maintenance is minimizing maintenance costs and downtime to keep equipment operating as designed. MIL-HDBK-338: Maintenance-All actions necessary for retaining April an item 18, 2006 in or restoring it to a specified condition. 2

3 5 Business Is? Business is all about making money. This is a balance between avoiding failures, repairing failures, and keeping the process operating to make money. In the end, reliability and maintenance are all about money. The ultimate aim of business is satisfying customers with on-time deliveries of quality products while producing a satisfactory long-term return for stockholders. 6 Which Is More Important? In business: The process is the king big $ s! The pawns are the equipment little $ s. For the business you must think: Top down Prioritize by use of $ Pareto distributions Unemotionally rather than love affairs Protect the money stream 3

4 7 Engineers Are---? Reliability Engineers-Strategic Assets Dedicated to mainly preventing failures Maintenance Engineers-Tactical Assets Dedicated to mainly correcting failures You need ~10 Maintenance Engineers to every 1 Reliability Engineer No increase in plant head count Need job descriptions?: 8 Get Organized Most mangers talk about reliability but emphasize maintenance they cross communicate!! Get your organization right Get your emphasis right say the right things Get your motivation right what s the reward? Be consistent no wishy-washy positions! Work for long terms improvements Work your Pareto list based on $ s 4

5 9 Attack Problems Top Down You ve got to know where to attack & what to do Do you accept the risk of failure? $Risk = (probability of failure)*$consequence of failure This is the do-nothing case. Can you afford it? What are your alternatives? Price out the details say it in $ s. Do you reject the risk of failure? Measure your alternatives against the do nothing case Don t take too much risk. You can t afford the exposure. Don t take too little risk. Timidity waste money. What s your personal risk allowance?: See your April SAP 18, 2006 signature authority. Where To Improve Go for the money not your love affair! Does the system need improvement? Does a device need improvement? Does a component need improvement? What are your alternatives? say it with money Can you avoid the big $ problems by an alternative called redundancy think of the Gordian knot solution 10 5

6 11 Best Place For Gains? Improve people performance ~38% of problems Make it easy for people to do right & hard to do wrong Improve procedures and practices ~34% Write it down correctly and train, train, train Improve hardware ~28% of problems Hardware problems may disappear if above corrected Engineers, by nature, think reliability issues are resolved with hardware and components and thus they often work on the wrong issues! The Pump Curve Issue 12 % Head Poor BEP = Best Efficiency Point This is the correct point for achieving the greatest inherent life for the pump System Resistance Curve Desired Excellent Intrinsic reliability-- is achieved at BEP (and measured by mean time to failure) Poor Centrifugal pump curves are NOT useful for the entire curve. To get long life, only a portion of the curve is useful! Poor Example Of System Resistance Curve Desired Pump Curve % Flow 6

7 Pump Curve Practices 13 % Head Low Flow Cavitation High Temperature Rise Low Bearing & Low Seal Life Lower Impeller Life BEP Better Practice = -20% to +10% Good (Commercial) Practice = -30% to +15% Avoid!! Suction Recirculation + Discharge Recirculation Best Practice = -10% to +5% of BEP + Low Bearing & Low Seal Life Cavitation Characteristic Life ~MTBF % Reliability η 0.92 η 0.53 η 0.1 η Reliability Curve Pump Curve % Flow Pump Practices vs Life L/D Pump Rotational Suction Piping Rotational Foundation Do Curve % Shaft Grouting Straight Alignment Balance Design Off BEP Alignment Runs Monolithic Resulting + 5% to ± Times L/D = ±0.003 inch Smooth at And Best Practices eta -10% of inches/inch Equipment 10 to 12 error ips Adhesive Multiplier BEP error Mass Epoxy Impeller % 100% 100% 100% 100% 100% 100% Housing % 100% 100% 100% 100% 100% 100% Pump Bearings % 100% 100% 100% 99% 100% 100% Barringer & Associates, Inc Mech. Seal % 99% 100% 100% 100% 100% 100% Bearing Seal % 99% 100% 100% 100% L/D 100% 100% Shaft % 100% 100% 100% Pump 99% Rotational Suction 100% Piping 100% Rotational Foundation Coupling % 100% 99% 100% Curve % 100% Shaft 100% 100% Grouting Maybe Straight Alignment Balance Design BEP Off Alignment Motor Bearings % 100% 100% 100% 100% Runs 100% 100% Replacement Mtr % 100% 99% 100% 100% 100% 100% Resulting + 10% to ± Times Slightly Motor Starter % 100% 100% 100% 100% 100% 100% L/D = ±0.010 inch Good at Better Practices eta -20% of inches/inch Equipment Pourous But 6 to 8 error ips Multiplier BEP error Mass Adhesive 14 Reliability practices must be connected with costs to find the lowest long term cost of ownership calculated by net present value. Impeller % 95% 95% 94% 95% 95% 98% Housing % 95% 95% 92% 95% 95% 95% Pump Bearings % 90% 88% 88% 90% 90% 90% Mech. Seal % 90% 90% 84% 90% L/D 90% 90% Pump Rotational Bearing Seal % 90% 90% 84% Suction 90% 90% Piping 90% Rotational Foundation Curve % Shaft Grouting Shaft % 90% Avoid! 88% 88% Straight 90% 90% Alignment 90% Balance Design BEP Off Alignment Coupling % 95% 90% 94% 95% Runs 90% 91% Motor Bearings % 93% 94% 97% 95% 90% 90% 0.5 Times Resulting +15% to ±0.009 Cementitous Replacement Mtr % 100% 100% 100% 100% L/D = 99% ± % Rough at Equipment Good Practices eta -30% of inches/inch & Low 3 Motor Starter % 100% 100% 100% 100% 1 to 100% inches 100% error ips Mass or Stilt- Multiplier BEP error Adhesion Mounted Impeller % 75% 90% 69% 81% 88% 88% Housing % 80% 83% 64% 79% 78% 80% Pump Bearings % 60% 58% 40% 61% 50% 55% Mech. Seal % 60% 58% 40% 61% 50% 55% Bearing Seal % 60% 40% 40% 64% 55% 55% Shaft % 60% 58% 40% 61% 50% 55% Coupling % 80% 65% 71% 78% 70% 75% Motor Bearings % 80% 55% 80% 75% 60% 60% Replacement Mtr % 100% 100% 100% 100% 100% 100% Motor Starter % 100% 100% 100% 100% 100% 100% 7

8 15 Summary Get your reliability program right Think about reliability issues strategically Look for gains first via people, second by processes and procedures, and last by way of components many component issues disappear when people/processes/procedure issues are solved to achieve inherent component reliability! Make money decisions watch your love affairs! 8